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		<title>three.js webgl - shaders - sky sun shader</title>
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		<div id="info"><a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> webgl - sky + sun shader
		</div>

		<script type="importmap">
			{
				"imports": {
					"three": "../build/three.module.js",
					"three/addons/": "./jsm/"
				}
			}
		</script>

		<script type="module">

			import * as THREE from 'three';

			import { GUI } from 'three/addons/libs/lil-gui.module.min.js';
			import { OrbitControls } from 'three/addons/controls/OrbitControls.js';
			import { Sky } from 'three/addons/objects/Sky.js';

			let camera, scene, renderer;

			let sky, sun;

			init();
			render();

			function initSky() {

				// Add Sky
				sky = new Sky();
				sky.scale.setScalar( 450000 );
				scene.add( sky );

				sun = new THREE.Vector3();

				/// GUI

				const effectController = {
					turbidity: 10,
					rayleigh: 3,
					mieCoefficient: 0.005,
					mieDirectionalG: 0.7,
					elevation: 2,
					azimuth: 180,
					exposure: renderer.toneMappingExposure
				};

				function guiChanged() {

					const uniforms = sky.material.uniforms;
					uniforms[ 'turbidity' ].value = effectController.turbidity;
					uniforms[ 'rayleigh' ].value = effectController.rayleigh;
					uniforms[ 'mieCoefficient' ].value = effectController.mieCoefficient;
					uniforms[ 'mieDirectionalG' ].value = effectController.mieDirectionalG;

					const phi = THREE.MathUtils.degToRad( 90 - effectController.elevation );
					const theta = THREE.MathUtils.degToRad( effectController.azimuth );

					sun.setFromSphericalCoords( 1, phi, theta );

					uniforms[ 'sunPosition' ].value.copy( sun );

					renderer.toneMappingExposure = effectController.exposure;
					renderer.render( scene, camera );

				}

				const gui = new GUI();

				gui.add( effectController, 'turbidity', 0.0, 20.0, 0.1 ).onChange( guiChanged );
				gui.add( effectController, 'rayleigh', 0.0, 4, 0.001 ).onChange( guiChanged );
				gui.add( effectController, 'mieCoefficient', 0.0, 0.1, 0.001 ).onChange( guiChanged );
				gui.add( effectController, 'mieDirectionalG', 0.0, 1, 0.001 ).onChange( guiChanged );
				gui.add( effectController, 'elevation', 0, 90, 0.1 ).onChange( guiChanged );
				gui.add( effectController, 'azimuth', - 180, 180, 0.1 ).onChange( guiChanged );
				gui.add( effectController, 'exposure', 0, 1, 0.0001 ).onChange( guiChanged );

				guiChanged();

			}

			function init() {

				camera = new THREE.PerspectiveCamera( 60, window.innerWidth / window.innerHeight, 100, 2000000 );
				camera.position.set( 0, 100, 2000 );

				scene = new THREE.Scene();

				const helper = new THREE.GridHelper( 10000, 2, 0xffffff, 0xffffff );
				scene.add( helper );

				renderer = new THREE.WebGLRenderer();
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( window.innerWidth, window.innerHeight );
				renderer.toneMapping = THREE.ACESFilmicToneMapping;
				renderer.toneMappingExposure = 0.5;
				document.body.appendChild( renderer.domElement );

				const controls = new OrbitControls( camera, renderer.domElement );
				controls.addEventListener( 'change', render );
				//controls.maxPolarAngle = Math.PI / 2;
				controls.enableZoom = false;
				controls.enablePan = false;

				initSky();

				window.addEventListener( 'resize', onWindowResize );

			}

			function onWindowResize() {

				camera.aspect = window.innerWidth / window.innerHeight;
				camera.updateProjectionMatrix();

				renderer.setSize( window.innerWidth, window.innerHeight );

				render();

			}

			function render() {

				renderer.render( scene, camera );

			}

		</script>

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